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Clean up some LoggingContext stuff (#7120)

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* Pull Sentinel out of LoggingContext

... and drop a few unnecessary references to it

* Factor out LoggingContext.current_context

move `current_context` and `set_context` out to top-level functions.

Mostly this means that I can more easily trace what's actually referring to
LoggingContext, but I think it's generally neater.

* move copy-to-parent into `stop`

this really just makes `start` and `stop` more symetric. It also means that it
behaves correctly if you manually `set_log_context` rather than using the
context manager.

* Replace `LoggingContext.alive` with `finished`

Turn `alive` into `finished` and make it a bit better defined.
This commit is contained in:
Richard van der Hoff 2020-03-24 14:45:33 +00:00 • committed by GitHub
parent 1fcf9c6f95
commit 39230d2171
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24 changed files with 232 additions and 222 deletions
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234
synapse/logging/context.py
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@ -175,7 +175,54 @@ class ContextResourceUsage(object):
return res
LoggingContextOrSentinel = Union["LoggingContext", "LoggingContext.Sentinel"]
LoggingContextOrSentinel = Union["LoggingContext", "_Sentinel"]
class _Sentinel(object):
"""Sentinel to represent the root context"""
__slots__ = ["previous_context", "finished", "request", "scope", "tag"]
def __init__(self) -> None:
# Minimal set for compatibility with LoggingContext
self.previous_context = None
self.finished = False
self.request = None
self.scope = None
self.tag = None
def __str__(self):
return "sentinel"
def copy_to(self, record):
pass
def copy_to_twisted_log_entry(self, record):
record["request"] = None
record["scope"] = None
def start(self):
pass
def stop(self):
pass
def add_database_transaction(self, duration_sec):
pass
def add_database_scheduled(self, sched_sec):
pass
def record_event_fetch(self, event_count):
pass
def __nonzero__(self):
return False
__bool__ = __nonzero__ # python3
SENTINEL_CONTEXT = _Sentinel()
class LoggingContext(object):
@ -199,76 +246,33 @@ class LoggingContext(object):
"_resource_usage",
"usage_start",
"main_thread",
"alive",
"finished",
"request",
"tag",
"scope",
]
thread_local = threading.local()
class Sentinel(object):
"""Sentinel to represent the root context"""
__slots__ = ["previous_context", "alive", "request", "scope", "tag"]
def __init__(self) -> None:
# Minimal set for compatibility with LoggingContext
self.previous_context = None
self.alive = None
self.request = None
self.scope = None
self.tag = None
def __str__(self):
return "sentinel"
def copy_to(self, record):
pass
def copy_to_twisted_log_entry(self, record):
record["request"] = None
record["scope"] = None
def start(self):
pass
def stop(self):
pass
def add_database_transaction(self, duration_sec):
pass
def add_database_scheduled(self, sched_sec):
pass
def record_event_fetch(self, event_count):
pass
def __nonzero__(self):
return False
__bool__ = __nonzero__ # python3
sentinel = Sentinel()
def __init__(self, name=None, parent_context=None, request=None) -> None:
self.previous_context = LoggingContext.current_context()
self.previous_context = current_context()
self.name = name
# track the resources used by this context so far
self._resource_usage = ContextResourceUsage()
# If alive has the thread resource usage when the logcontext last
# became active.
# The thread resource usage when the logcontext became active. None
# if the context is not currently active.
self.usage_start = None
self.main_thread = get_thread_id()
self.request = None
self.tag = ""
self.alive = True
self.scope = None # type: Optional[_LogContextScope]
# keep track of whether we have hit the __exit__ block for this context
# (suggesting that the the thing that created the context thinks it should
# be finished, and that re-activating it would suggest an error).
self.finished = False
self.parent_context = parent_context
if self.parent_context is not None:
@ -283,44 +287,15 @@ class LoggingContext(object):
return str(self.request)
return "%s@%x" % (self.name, id(self))
@classmethod
def current_context(cls) -> LoggingContextOrSentinel:
"""Get the current logging context from thread local storage
Returns:
LoggingContext: the current logging context
"""
return getattr(cls.thread_local, "current_context", cls.sentinel)
@classmethod
def set_current_context(
cls, context: LoggingContextOrSentinel
) -> LoggingContextOrSentinel:
"""Set the current logging context in thread local storage
Args:
context(LoggingContext): The context to activate.
Returns:
The context that was previously active
"""
current = cls.current_context()
if current is not context:
current.stop()
cls.thread_local.current_context = context
context.start()
return current
def __enter__(self) -> "LoggingContext":
"""Enters this logging context into thread local storage"""
old_context = self.set_current_context(self)
old_context = set_current_context(self)
if self.previous_context != old_context:
logger.warning(
"Expected previous context %r, found %r",
self.previous_context,
old_context,
)
self.alive = True
return self
def __exit__(self, type, value, traceback) -> None:
@ -329,24 +304,19 @@ class LoggingContext(object):
Returns:
None to avoid suppressing any exceptions that were thrown.
"""
current = self.set_current_context(self.previous_context)
current = set_current_context(self.previous_context)
if current is not self:
if current is self.sentinel:
if current is SENTINEL_CONTEXT:
logger.warning("Expected logging context %s was lost", self)
else:
logger.warning(
"Expected logging context %s but found %s", self, current
)
self.alive = False
# if we have a parent, pass our CPU usage stats on
if self.parent_context is not None and hasattr(
self.parent_context, "_resource_usage"
):
self.parent_context._resource_usage += self._resource_usage
# reset them in case we get entered again
self._resource_usage.reset()
# the fact that we are here suggests that the caller thinks that everything
# is done and dusted for this logcontext, and further activity will not get
# recorded against the correct metrics.
self.finished = True
def copy_to(self, record) -> None:
"""Copy logging fields from this context to a log record or
@ -371,9 +341,14 @@ class LoggingContext(object):
logger.warning("Started logcontext %s on different thread", self)
return
if self.finished:
logger.warning("Re-starting finished log context %s", self)
# If we haven't already started record the thread resource usage so
# far
if not self.usage_start:
if self.usage_start:
logger.warning("Re-starting already-active log context %s", self)
else:
self.usage_start = get_thread_resource_usage()
def stop(self) -> None:
@ -396,6 +371,15 @@ class LoggingContext(object):
self.usage_start = None
# if we have a parent, pass our CPU usage stats on
if self.parent_context is not None and hasattr(
self.parent_context, "_resource_usage"
):
self.parent_context._resource_usage += self._resource_usage
# reset them in case we get entered again
self._resource_usage.reset()
def get_resource_usage(self) -> ContextResourceUsage:
"""Get resources used by this logcontext so far.
@ -409,7 +393,7 @@ class LoggingContext(object):
# If we are on the correct thread and we're currently running then we
# can include resource usage so far.
is_main_thread = get_thread_id() == self.main_thread
if self.alive and self.usage_start and is_main_thread:
if self.usage_start and is_main_thread:
utime_delta, stime_delta = self._get_cputime()
res.ru_utime += utime_delta
res.ru_stime += stime_delta
@ -492,7 +476,7 @@ class LoggingContextFilter(logging.Filter):
Returns:
True to include the record in the log output.
"""
context = LoggingContext.current_context()
context = current_context()
for key, value in self.defaults.items():
setattr(record, key, value)
@ -512,27 +496,24 @@ class PreserveLoggingContext(object):
__slots__ = ["current_context", "new_context", "has_parent"]
def __init__(self, new_context: Optional[LoggingContextOrSentinel] = None) -> None:
if new_context is None:
self.new_context = LoggingContext.sentinel # type: LoggingContextOrSentinel
else:
self.new_context = new_context
def __init__(
self, new_context: LoggingContextOrSentinel = SENTINEL_CONTEXT
) -> None:
self.new_context = new_context
def __enter__(self) -> None:
"""Captures the current logging context"""
self.current_context = LoggingContext.set_current_context(self.new_context)
self.current_context = set_current_context(self.new_context)
if self.current_context:
self.has_parent = self.current_context.previous_context is not None
if not self.current_context.alive:
logger.debug("Entering dead context: %s", self.current_context)
def __exit__(self, type, value, traceback) -> None:
"""Restores the current logging context"""
context = LoggingContext.set_current_context(self.current_context)
context = set_current_context(self.current_context)
if context != self.new_context:
if context is LoggingContext.sentinel:
if not context:
logger.warning("Expected logging context %s was lost", self.new_context)
else:
logger.warning(
@ -541,9 +522,30 @@ class PreserveLoggingContext(object):
context,
)
if self.current_context is not LoggingContext.sentinel:
if not self.current_context.alive:
logger.debug("Restoring dead context: %s", self.current_context)
_thread_local = threading.local()
_thread_local.current_context = SENTINEL_CONTEXT
def current_context() -> LoggingContextOrSentinel:
"""Get the current logging context from thread local storage"""
return getattr(_thread_local, "current_context", SENTINEL_CONTEXT)
def set_current_context(context: LoggingContextOrSentinel) -> LoggingContextOrSentinel:
"""Set the current logging context in thread local storage
Args:
context(LoggingContext): The context to activate.
Returns:
The context that was previously active
"""
current = current_context()
if current is not context:
current.stop()
_thread_local.current_context = context
context.start()
return current
def nested_logging_context(
@ -572,7 +574,7 @@ def nested_logging_context(
if parent_context is not None:
context = parent_context # type: LoggingContextOrSentinel
else:
context = LoggingContext.current_context()
context = current_context()
return LoggingContext(
parent_context=context, request=str(context.request) + "-" + suffix
)
@ -604,7 +606,7 @@ def run_in_background(f, *args, **kwargs):
CRITICAL error about an unhandled error will be logged without much
indication about where it came from.
"""
current = LoggingContext.current_context()
current = current_context()
try:
res = f(*args, **kwargs)
except: # noqa: E722
@ -625,7 +627,7 @@ def run_in_background(f, *args, **kwargs):
# The function may have reset the context before returning, so
# we need to restore it now.
ctx = LoggingContext.set_current_context(current)
ctx = set_current_context(current)
# The original context will be restored when the deferred
# completes, but there is nothing waiting for it, so it will
@ -674,7 +676,7 @@ def make_deferred_yieldable(deferred):
# ok, we can't be sure that a yield won't block, so let's reset the
# logcontext, and add a callback to the deferred to restore it.
prev_context = LoggingContext.set_current_context(LoggingContext.sentinel)
prev_context = set_current_context(SENTINEL_CONTEXT)
deferred.addBoth(_set_context_cb, prev_context)
return deferred
@ -684,7 +686,7 @@ ResultT = TypeVar("ResultT")
def _set_context_cb(result: ResultT, context: LoggingContext) -> ResultT:
"""A callback function which just sets the logging context"""
LoggingContext.set_current_context(context)
set_current_context(context)
return result
@ -752,7 +754,7 @@ def defer_to_threadpool(reactor, threadpool, f, *args, **kwargs):
Deferred: A Deferred which fires a callback with the result of `f`, or an
errback if `f` throws an exception.
"""
logcontext = LoggingContext.current_context()
logcontext = current_context()
def g():
with LoggingContext(parent_context=logcontext):